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=head1 NAME GLwDrawingArea, GLwMDrawingArea - Open GL drawing widgets. =head1 SYNOPSIS #include <GL/GLwDrawA.h> widget = XtCreateWidget(widget, glwDrawingAreaWidgetClass, ...); ld ... -lGLw -l<anywidgetlibrary> -lXt -lGL -lX11 ... #include <GL/GLwMDrawA.h> widget = XtCreateWidget(widget, glwMDrawingAreaWidgetClass, ...); ld ... -lGLw -lXm -lXt -lGL -lX11 ... =head1 DESCRIPTION I<GLwDrawingArea> and I<GLwMDrawingArea> are widgets suitable for Open GL drawing. They provide a window with the appropriate visual and colormaps needed for open GL, based on supplied parameters. I<GLwDrawingArea> and I<GLwMDrawingArea> also provide callbacks for redraw, resize, input, and initialization. I<GLwDrawingArea> is not a part of any widget set, but depends only on Xt. I<GLwDrawingArea> can be used with any widget set. I<GLwMDrawingArea> is identical to I<GLwDrawingArea> except that it is a subclass of the Motif widget class I<XmPrimitive> and has resources and defaults suitable for use with Motif. For example, I<GLwMDrawingArea> provides the default Motif background and foreground colors for resources, and deals better with keyboard traversal. Although the I<GLwDrawingArea> widget can be used in a Motif program, it is recommended that I<GLwMDrawingArea> be used instead. Since both I<GLwDrawingArea> and I<GLwMDrawingArea> widgets behave almost identically, the remainder of this manual page will refer only to I<GLwDrawingArea>, except when the behaviors differ. Unless explicitly stated, all statements about I<GLwDrawingArea> also apply to I<GLwMDrawingArea>. Among the information provided when creating a I<GLwDrawingArea> is information necessary to determine the visual. This may be provided in three ways, all of them through resources. A specific visualInfo structure may be passed in. (This visualInfo must have been obtained elsewhere; it is the application designer's responsibility to make sure that it is compatible with the open GL rendering done by the application). Alternatively, an attribute list may be provided. This attribute list is formatted identically to that used for direct open GL programming. Finally, each attribute can be specified as an individual resource. The latter method is the simplest, and is the only method that works from resource files. In addition to allocating the visual, the I<GLwDrawingArea> will also allocate the colormap unless one is provided by the application. (If one is provided it is the application writer's responsibility to guarantee compatibility between the colormap and the visual). If an application creates multiple I<GLwDrawingAreas> are created in the same visual, the same colormap will be used. (However the colormap will not be shared among separate applications). Creating the widget does not actually create the window until it is realized, and consequently, the application should not perform any open GL operations to the window immediately after creation. Instead the application must wait until after it has realized the window. Alternatively, the ginit callback may be used to indicate when the window has been created. Upon receiving this callback, the application can perform all open GL initialization for the window, and can subsequently perform other operations on it. The initialization is discussed in more detail below. Applications select which I<GLwDrawingArea> they are accessing using either I<glXMakeCurrent> or the convenience function I<GLwDrawingAreaMakeCurrent> which uses a widget instead of a display and window. If there is only one I<GLwDrawingArea> this need only be called once, however if there is more than one I<GLwDrawingArea> it should be called at the start of each callback. Callbacks in this case include not only callbacks provided by the widget itself, but any other callback that leads to GL activity such as a timeout or a workproc. If an application is using double buffering, it may call I<GLwDrawingAreaSwapBuffers> instead of I<glXSwapBuffers>. This allows the use of the widget instead of the display and window. =head2 GLwDrawingArea Classes I<GLwDrawingArea> inherits behavior and resources from the Core class. The class pointer is I<GLwDrawingAreaClass>. The class name is I<GLwDrawingArea>. =head2 GLwMDrawingArea Classes I<GLwMDrawingArea> inherits behavior and resources from the I<XmPrimitive> and Core classes. The class pointer is I<GLwMDrawingAreaClass>. The class name is I<GLwMDrawingArea>. =head2 New Resources The following tables define a set of widget resources used by the programmer to specify data. The programmer can also set the resource values for the inherited classes to set attributes for this widget. To reference a resource by name or by class in a .Xdefaults file, remove the I<GLwN> or I<GLwC> prefix and use the remaining letters. There are two tables included. The first table includes resources that correspond directly to the attributes used by I<glXChooseVisual>. As with I<glXChooseVisual>, all Boolean resources default to FALSE and all integer resources default to 0. These resources can all be set only at creation time, and are used to determine the visual. If either the I<GLwNattribList> or I<GLwNvisualInfo> resource is set, these resources are ignored. The specific meaning of these resources is discussed in the I<glXChooseVisual> manual page and will not be discussed here. ___________________________________________________________________________ | | | | | | Name | Class | Type | OpenGL attribute | |____________________|____________________|_________|______________________| | | | | | | GLwNbufferSize | GLwCBufferSize | int | GLX_BUFFER_SIZE | |____________________|____________________|_________|______________________| | | | | | | GLwNlevel | GLwCLevel | int | GLX_LEVEL | |____________________|____________________|_________|______________________| | | | | | | GLwNrgba | GLwCRgba | Boolean | GLX_RGBA | |____________________|____________________|_________|______________________| | | | | | | GLwdoublebuffer | GLwCDoublebuffer | Boolean | GLX_DOUBLEBUFFER | |____________________|____________________|_________|______________________| | | | | | | GLwNstereo | GLwCStereo | Boolean | GLX_STEREO | |____________________|____________________|_________|______________________| | | | | | | GLwNauxBuffers | GLwCAuxBuffers | Boolean | GLX_AUX_BUFFERS | |____________________|____________________|_________|______________________| | | | | | | GLwNredSize | GLwCColorSize | int | GLX_RED_SIZE | |____________________|____________________|_________|______________________| | | | | | | GLwNgreenSize | GLwCColorSize | int | GLX_GREEN_SIZE | |____________________|____________________|_________|______________________| | | | | | | GLwNblueSize | GLwCColorSize | int | GLX_BLUE_SIZE | |____________________|____________________|_________|______________________| | | | | | | GLwNalphaSize | GLwCAlphaSize | int | GLX_ALPHA_SIZE | |____________________|____________________|_________|______________________| | | | | | | GLwNDepthSize | GLwCDepthSize | int | GLX_DEPTH_SIZE | |____________________|____________________|_________|______________________| | | | | | | GLwNStencilSize | GLwCStencilSize | int | GLX_STENCIL_SIZE | |____________________|____________________|_________|______________________| | | | | | | GLwNaccumRedSize | GLwCAccumColorSize | int | GLX_ACCUM_RED_SIZE | |____________________|____________________|_________|______________________| | | | | | | GLwNaccumGreenSize | GLwCAccumColorSize | int | GLX_ACCUM_GREEN_SIZE | |____________________|____________________|_________|______________________| | | | | | | GLwNaccumBlueSize | GLwCAccumColorSize | int | GLX_ACCUM_BLUE_SIZE | |____________________|____________________|_________|______________________| | | | | | | GLwNaccumAlphaSize | GLwCAccumAlphaSize | int | GLX_ACCUM_ALPHA_SIZE | |____________________|____________________|_________|______________________| The following table lists other resources of the I<GLwDrawingArea> widget. each of these will be described subsequently The codes in the access column indicate if the given resource can be set at creation time (C), set by using I<XtSetValues> (S), retrieved by using I<XtGetValues> (G), or is not applicable (N/A). ______________________________________________________________________________________ | | | | | | | Name | Class | Type | Default | Access | |_________________________|_______________________|________________|_________|________| | | | | | | | GLwNallocateBackground | GLwCAllocateColors | Boolean | FALSE | CG | |_________________________|_______________________|________________|_________|________| | | | | | | | GLwNallocateOtherColors | GLwCAllocateColors | Boolean | FALSE | CG | |_________________________|_______________________|________________|_________|________| | | | | | | | GLwNattribList | GLwCAttribList | int * | NULL | CG | |_________________________|_______________________|________________|_________|________| | | | | | | | GLwNexposeCallback | GLwCCallback | XtCallbackList | NULL | C | |_________________________|_______________________|________________|_________|________| | | | | | | | GLwNginitCallback | GLwCCallback | XtCallbackList | NULL | C | |_________________________|_______________________|________________|_________|________| | | | | | | | GLwNinputCallback | GLwCCallback | XtCallbackList | NULL | C | |_________________________|_______________________|________________|_________|________| | | | | | | | GLwNinstallBackground | GLwCInstallBackground | Boolean | TRUE | CG | |_________________________|_______________________|________________|_________|________| | | | | | | | GLwNinstallColormap | GLwCInstallColormap | Boolean | TRUE | CG | |_________________________|_______________________|________________|_________|________| | | | | | | | GLwNresizeCallback | GLwCCallback | XtCallbackList | NULL | C | |_________________________|_______________________|________________|_________|________| | | | | | | | GLwNvisualInfo | GLwCVisualInfo | XVisualInfo* | NULL | CG | |_________________________|_______________________|________________|_________|________| =over 4 =item GLwNallocateBackground B<[Caveat: This resource is not honored yet.]> If TRUE, the background pixel and pixmap will be allocated if appropriate using the newly calculated colormap and visual. If FALSE, they will retain values calculated using the parent's colormap and visual. Applications which wish to have X clear their background for them will usually set this to TRUE. Applications clearing their own background will often set this to FALSE, although they may set this to TRUE if they query the background for their own use. One reason to leave this resource FALSE is that if color index mode is in use this avoid using up a pixel from the newly allocated colormap. Also, on hardware that supports only one colormap, the application may need to do more careful color allocation to avoid flashing between the openGL colormap and the default X colormap. (Note that because of the way Xt works, the background colors are originally calculated using the default colormap; if this resource is set they can be recalculated correctly. If a colormap was explicitly supplied to the widget rather than being dynamically calculated, these resources are always calculated using that colormap.) =item GLwNallocateOtherColors B<[Caveat: This resource is not honored yet.]> This is similar to I<GLwNallocateBackground>, but allocates other colors normally allocated by widgets. Although the I<GLwDrawingArea> and I<GLwMDrawingArea> widget do not make use of these colors the application may choose to query them. For the non-Motif I<GLwDrawingArea> widget there are no other colors allocated, so this resource is a no-op. For the Motif I<GLwMDrawingArea> are widget, the I<XmPrimitive> resources I<XmNforeground>, I<XmNhighlightColor>, and I<XmNhighlightPixmap> are calculated. =item GLwNattribList Contains the list of attributes suitable for a call to I<glXChooseVisual>. If this resource is NULL, it is calculated based on the attribute resources. If it is not NULL, the attribute resources are ignored. =item GLwNexposeCallback Specifies the list of callbacks that is called when the widget receives an exposure event. The callback reason is I<GLwCR_EXPOSE>. The callback structure also includes the exposure event. The application will generally want to redraw the scene. =item GLwNginitCallback Specifies the list of callbacks that is called when the widget is first realized. Since no open GL operations can be done before the widget is realized, this callback can be used to perform any appropriate open GL initialization such as creating a context. The callback reason is I<GLwCR_GINIT>. =item GLwNinputCallback Specifies the list of callbacks that is called when the widget receives a keyboard or mouse event. By default, the input callback is called on each key press and key release, on each mouse button press and release, and whenever the mouse is moved while a button is pressed. However this can be changed by providing a different translation table. The callback structure also includes the input event. The callback reason is I<GLwCR_INPUT>. The input callback is provided as a programming convenience, as it provides a convenient way to catch all input events. However, a more modular program can often be obtained by providing specific actions and translations in the application rather than using a single catch all callback. Use of explicit translations can also provide for more customizability. =item GLwNinstallBackground B<[Caveat: This resource is not honored yet.]> If set to TRUE, the background is installed on the window. If set to FALSE, the window has no background. This resource has no effect unless I<GLwNallocateBackground> is also TRUE. =item GLwNinstallColormap If set to TRUE, the widget will call I<XSetWMColormapWindows> to tell the window manager to install the colormap when the window's shell has focus. If set to FALSE, this will not be called. For applications with multiple I<GLwDrawingAreas> sharing a single colormap, it is most efficient to set this resource to TRUE for exactly one I<GLwDrawingArea> with each colormap. If an application needs additional control over the order of colormaps, this resource can be set to FALSE, with the application calling I<XSetWMColormapWindows> explicitly. =item GLwNresizeCallback Specifies the list of callbacks that is called when the I<GLwDrawingArea> is resized. The callback reason is I<GLwCR_RESIZE>. =item GLwNvisualInfo Contains a pointer to the window's visual info structure. If NULL, the visualInfo is calculated at widget creation time based on the I<GLwNattributeList> resource (which is itself calculated from the various resources). If I<GLwNvisualInfo> is not NULL the I<GLwNattributList> and the attribute resources are ignored. =back =head2 Inherited Resources B<[Caveat: The colormap and background resources do not receive special treatment yet.]> Both I<GLwDrawingArea> and I<GLwMDrawingArea> inherit behavior and resources from the core superclass. Other than the behavior of the colormap and background resources described previously, all defaults are the same as for core. In addition, the Motif version I<GLwMDrawingArea> also inherits from I<XmPrimitive>. The behavior of the color resources has been described previously. The TraversalOn resource is disabled for this widget, but if keyboard input is required it should be enabled. (Also, the application should call C<XmProcessTraversal(widget, XmTRAVERSE_CURRENT)> whenever mouse button 1 is clicked in the widget. This is similar to the requirements of the Motif Drawing area.) Because Motif gets confused by having multiple visuals in one top level shell, I<XmNhighlightOnEnter> has been disabled, and I<XmNhighlightThickness> has been set to 0. =head2 Callback Information A pointer to the following structure is passed to each callback: typedef struct { int reason; XEvent * event; Dimensionwidth, height; } GLwDrawingAreaCallbackStruct; =over 4 =item reason Indicates why the callback was invoked. Appropriate values are stated in the above resource descriptions. For Motif programmers, the values I<GLwCR_EXPOSE>, I<GLwCR_RESIZE>, and I<GLwCR_INPUT> are equal to I<XmCR_EXPOSE>, I<XmCR_RESIZE>, and I<XmCR_INPUT> respectively. I<GLwCR_GINIT> does not have a Motif equivalent. =item event Points to the XEvent that triggered the callback. This is NULL for I<GLwNginitCallback> and I<GLwNresizeCallback>. =item width =item height Are set to the width and height of the window. =back =head2 Translations I<GLwDrawingArea> has the translations listed below. <KeyDown>: glwInput() <KeyUp>: glwInput() <BtnDown>: glwInput() <BtnUp>: glwInput() <BtnMotion>: glwInput() I<GLwMDrawingArea> has the following additional translation: <Key>osfHelp: PrimitiveHelp() An application wishing to catch other events than these defaults can do so by installing a different translation table. =head2 Action Routines The I<GLwDrawingArea> has the following action routine: =over 4 =item glwInput() Called whenever one of the above translations specifies that input has occurred. Its sole purpose is to call the input callback. =back =head1 INITIALIZATION When the widget is initially created (e.g. through I<XtCreateWidget>(3X)) the associated window is not actually created. Instead, window creation is delayed until the widget is realized. However, I<glXchooseVisual> is called immediately, so information based on its results is available. Between the time the widget is created and it is realized, the following apply: =over 4 =item No open GL operations can be done to the window =item No resize callbacks are generated. =item The normal window is available (I<XtWindow> returns NULL). =item I<GLwDrawingAreaMakeCurrent> (and I<glXMakeCurrent>) should not be called. =back When the widget is realized, the following actions take place: =over 4 =item The window is created. =item The ginit callback is called. The user may use this callback to perform any needed open GL initialization to the window. =back =head1 NOTES When using the input callback to receive keyboard input, the keycode in the event must be converted to a KeySym. Use I<XLookupKeysym>(3X) or I<XLookupString>(3X) to do the conversion. Keyboard input can also be dealt using translations, in which case no such conversion is required. Motif programmers should keep in mind that OSF uses virtual bindings and replaces some of the key bindings. As a common example, if the ESC key is to be used to exit the program (as it often is in GL programs), the translation should specify <key>osfCancel instead of <key>Escape. Motif programmers may also create a I<GLwMDrawingArea> widget with the Motif style I<GLwCreateMDrawingArea>. =head1 EXAMPLE Here are some code fragments that create a I<GLwDrawingArea> widget, and manage the appropriate callbacks. #include <X11/GLW/GLwDrawingArea.h> static GLXContext glx_context; /* assume only one context */ . . . main() { Arg args[10]; int n; Widget parent;/* The parent of the gl widget */ Widget glw;/* The GLwDrawingArea widget */ . . . /* Create the widget using RGB mode. This can also be set * in an X Defaults file */ n = 0; XtSetArg(args[n], GLwNrgba, TRUE); n++; glw = XtCreateManagedWidget("glw", GLwDrawingAreaWidgetClass, parent, args, n); XtAddCallback(glw, GLwNexposeCallback, exposeCB, 0); XtAddCallback(glw, GLwNresizeCallback, resizeCB, 0); XtAddCallback(glw, GLwNginitCallback, ginitCB, 0); /* Also add input callback if needed */ . . . } static void exposeCB(Widget w, XtPointer client_data, GLwDrawingAreaCallbackStruct call_data) { GLwDrawingAreaMakeCurrent (w, glx_context); /* redraw the display */ } static void resizeCB(Widget w, XtPointer client_data, GLwDrawingAreaCallbackStruct call_data) { GLwDrawingAreaMakeCurrent (w, glx_context); /* perform any resize actions */ } static void ginitCB(Widget w, XtPointer client_data, GLwDrawingAreaCallbackStruct call_data) { Arg args[1]; XVisualInfo *vi; XtSetArg(args[0], GLwNvisualInfo, &vi); XtGetValues(w, args, 1); /* create a visual context */ glx_context = glXCreateContext(XtDisplay(w), vi, 0, GL_FALSE); GLwDrawingAreaMakeCurrent (w, glx_context); /* Perform any necessary graphics initialization.*/ } The Motif program need only differ by including GLwMDrawingArea.h instead of GLwDrawingArea.h and by creating a widget of type I<GLwMDrawingAreaWidgetClass> instead of I<GLwDrawingAreaWidgetClass>. As an alternative, the Motif program could use I<GLwCreateMDraw>(3X) instead. =head1 WARNINGS If a I<GLwDrawingArea> widget is created as a child of an already realized widget, the I<GLwDrawingArea> widget will be created immediately, without giving the user an opportunity to add the ginit callback. In such a case, initialization should be done immediately after creating the widget rather than by using the callback. If the non-Motif I<GLwDrawingArea> widget is used in a Motif program and keyboard traversal is attempted, the behavior is undefined if the user traverses into the I<GLwDrawingArea> widget. =head1 RELATED INFORMATION L<glXChooseVisual>, L<GLwDrawingAreaMakeCurrent>, L<glXMakeCurrent>, L<GLwDrawingAreaSwapBuffers>, L<GLwCreateMDraw>, L<Core>, L<XmPrimitive>, L<VirtualBindings>, L<Gflush>), L<XSetWMColormapWindows> and the Open GL spec. =head1 DATE $Id: GLwDrawingArea.pod,v 1.3 1995/04/11 23:42:06 ohl Exp $